Frontal sinus trephination (FST) has numerous applications in the
treatment of acute and chronic sinus disease. This procedure involves
making an incision at the medial aspect of the supraorbital rim and then
drilling the sinus's anterior table. Placement of a frontal
trephine allows for irrigation of the frontal recess in order to
evacuate the frontal sinus in a minimally invasive manner. Orbital
injury is a rare complication of FST. We present a case of previously
unreported orbital compartment syndrome secondary to iatrogenic fracture
of the superomedial orbital rim as a complication of frontal trephine
irrigation. We also review the literature on the applications of FST and
its associated complications, and we discuss orbital compartment
syndrome as a complication of sinus surgery.

Introduction

Several surgical approaches to the frontal sinus have been
described, including frontal sinusotomy, endoscopic endonasal
sinusotomy, and various combined approaches that involve both endoscopic
techniques and frontal sinus trephination (FST). In 1750, Runge (1)
first described the use of FST in treating complications of acute
frontal sinusitis, and its applications have expanded over time.

FST involves making an incision at the medial aspect of the
supraorbital rim and then drilling the frontal sinus's anterior
table. (2) Because direct endoscopic visualization of the frontal sinus
drainage pathway is veiled by the capricious and complex pneumatization
pattern of frontoethmoid cells, FST has been used as an adjunct to
endoscopic sinus surgery. It is useful for endonasally locating the
ostium and subsequently performing outflow tract enlargement. (3) FST
also enables frontal recess irrigation in order to evacuate the frontal
sinus in a minimally invasive and hence minimally traumatic manner. (3)
Significant advantages of a combined approach include reduced morbidity,
shorter recovery, and a greater likelihood of preserving sinus mucosa
and natural drainage outflow tracts. (2)

Minitrephination of the frontal sinus is associated with a
complication rate of 6.4%. (4) The most common is infection, which
accounts for approximately one-third of all complications. (4) Others
include postoperative stenosis, a poor aesthetic outcome and, in very
rare cases, intracranial or orbital penetration. Since FST carries a
greater risk of complication than does endoscopic sinus surgery alone,
it is reserved for cases in which adequate endoscopic access to and
exposure of the frontal recess are limited. (5)

We present a very unusual complication of FST: orbital compartment
syndrome. This syndrome occurred secondary to an iatrogenic
microfracture of the superomedial orbital rim. We describe its
management with emergency lateral canthotomy. To the best of our
knowledge, this type of complication has not been previously reported in
the literature in association with FST.

Case report

A 67-year-old woman presented with a long-standing history of
severe nasal polyposis. Her main symptoms were chronic severe headaches
and nasal congestion. Computed tomography (CT) showed a complete
opacification of the frontal, ethmoid, and sphenoid sinuses bilaterally;
these imaging characteristics were suggestive of allergic fungal disease
(figure, A). The patient was taken to the operating room for endoscopic
sinus surgery.

Intraoperatively, nasal polyps were cleared from the right nasal
cavity, and a complete ethmoidectomy was performed on the right. A right
frontal trephine was placed through the anterior frontal sinus table,
and fluorescein irrigation was used to wash out fungal mucin from the
right frontal sinus. Following this, a left frontal trephine was placed
through the anterior frontal sinus table and irrigated with
fluoresceinized saline to wash out the viscous fungal mucin. Irrigation
was noted to be more difficult on the left, but large amounts of fungus
were still expressed into the nose.

Before the left ethmoidectomy was started, bulging and tension of
the skin of the left upper eyelid developed. Chemosis was seen, and the
eye was clearly proptotic. No bleeding was noted in the nose, and the
ethmoid sinuses had not yet been dissected on that side, so an arterial
bleed was discounted as the cause. No reason for raised intraorbital
pressure was seen. An urgent lateral canthotomy was performed, which
rapidly reduced the tension on the eyelid, and the eye regained its
normal contour. The procedure was then aborted.

Postoperatively in the recovery room, the patient reported no
decrease in visual acuity or diplopia. An immediate CT was obtained, and
it showed a new fracture line in the superomedial orbital rim (figure,
B). The fracture was clearly located at a site distant from the site of
the trephine placement. Therefore, the fracture was presumably caused by
pressure from the trephine irrigation rather than by the placement of
the trephine itself.

The ophthalmology service was consulted to assist in ongoing
management, which consisted of regular vision checks and natural tear
irrigation. On postoperative day 5, a lateral canthopexy was performed
to resuspend the lower lid, and the patient was sent home.

Discussion

The optimal trephine diameter and placement location have been
evaluated and debated in the literature. A maximum diameter of 5 mm has
been recommended to minimize soft-tissue prolapse and cosmetic
deformity. (5)

Previously, the optimal location of trephine placement was
considered to be 10 mm from the midline at the level of the medial
aspect of the eyebrow. (6) However, a subsequent evaluation of the
safety of FST with standard frontal trephination instruments of 7 mm in
length revealed no significant difference between sinus depth at various
distances (5, 10, and 15 mm) from the midline. (3) Nevertheless, because
of the variability in the location of the intersinus septum among
individuals, the risk of crossed trephination is higher when the
trephine is placed closer to the midline. (3)

Once the trephine has been placed, aspiration with a saline-filled
syringe should be performed to ensure correct placement. The presence of
a clear aspirate may indicate intracranial penetration, which is an
indication that the trephine should be removed. (6) In nearly 15% of
patients with nonhypoplastic frontal sinuses, the depth at a particular
point from the midline may not be adequate, which increases the risk of
inadvertent entry through the sinus's posterior table. (3) Since
women have smaller frontal sinuses than do men, women represent the
majority of these patients. (3)

Regardless of the patient's sex, a detailed preoperative
review of CT images should be performed to ensure that the frontal sinus
is not too shallow for the trephination instrument. Sagittal
reconstructions of CT images best evaluate the anterorposterior
dimension of the frontal sinus, and they should be used in conjunction
with axial and coronal views. (2,3)

Other complications of FST include (1) supratrochlear and
supraorbital nerve and vessel injury with resultant hypoesthesia of the
ipsilateral forehead and scalp, (2) poor wound healing, and (3) possibly
hypertrophic scarring. (2) The risk of associated complications
increases with a more lateral incision, so the supraorbital nerve notch
should be palpated as a means of preventing this. (3) Superomedial
orbital injury can lead to hemorrhage and vision loss because the
ophthalmic artery courses through this area and branches into the
anterior and posterior ethmoid arteries.

Seiberling et al described two complications that occurred when a
trephine was placed into a frontal mucocele that had eroded the orbital
rim and lamina papyracea. (6) After trephine flushing, one patient
developed increased intraocular pressure and temporary proptosis, while
the other developed brief asystole secondary to activation of the ocular
carotid reflex. In view of these findings, if there is evidence of
erosion of the floor or posterior wall secondary to frontal disease,
fluorescein flushing must be performed judiciously. If resistance is
encountered or if the fluorescein is not visualized intranasally, it
should be stopped immediately.

An acute rise in intraorbital pressure is a hallmark of orbital
compartment syndrome. The onset of this syndrome represents a surgical
emergency that can develop in seconds to minutes. Its most common cause
is orbital hemorrhage. (4) The orbit contains extraocular muscles, fat,
the lacrimal gland and lacrimal apparatus, neurovascular structures, the
globe, and surrounding fascia. Anteriorly, the orbit is bounded by the
eyelids, orbital septum, and on three of its sides by four firm, bony
walls. Its volume of approximately 30 ml is fixed in nature. (7) Forward
movement of the globe and fat prolapse are compensatory mechanisms that
occur during acute increases in intraorbital pressure. However, forward
movement is limited by the medial and lateral canthal tendons that
attach the eyelids to the bony orbital rim. Consequently, a continuous
rise in intraorbital pressure begets a decrease in perfusion. (7)

Signs of orbital compartment syndrome can be categorized as
external, ophthalmoscopic, and neuro-opthalmic. (4)

Intraoperatively, external signs are most useful for detecting
raised intraocular pressure. Two of the earliest signs are acute
proptosis and a loss of orbital compliance. (4) Early recognition of
injury to the orbit and immediate intervention are required to prevent
serious, long-term ophthalmologic complications.

Since orbital compartment syndrome is a surgical emergency, an
ophthalmologist should be consulted immediately. Initially, cantholysis
should be performed, including both a lateral canthotomy and canthal
tendon disinsertion. In lateral canthotomy, the lateral canthal tendon
is cut along its length; in canthal tendon disinsertion, the lateral
canthal tendons inferior crus is disinserted from the tubercle of
Whitnall on the bony orbit. (8) In the management of orbital compartment
syndrome secondary to orbital hemorrhage, cantholysis has been shown to
lead to a significantly greater reduction in intraocular pressure than
that which can be accomplished by either lateral canthotomy or canthal
tendon disinsertion alone. (8)

Immediately following this procedure, the patients clinical status
should be reevaluated. If there is no improvement within a few minutes,
the surgeon should consider proceeding with disinsertion of the superior
canthal tendon, followed by transconjunctival or transcutaneous division
of the orbital septum from its attachment to the orbital rim. (9) If
these measures fail, extensive osseous decompression may be required.

The prognosis for patients with orbital compartment syndrome
depends on how much time has elapsed between onset and treatment, the
presence of globe tenting (which may predict visual compromise), the
patient's age, and the underlying etiology. (9) Findings on
postoperative orbital CT and magnetic resonance imaging correlate well
with the clinically localized site of injury and can assist in
elucidating the etiology of complications related to endoscopic sinus
surgery. (9)

From ENT Consultants, St. John's, Newfoundland (Dr. Angel);
and the Department of Diagnostic Radiology and Nuclear Imaging (Dr.
Zener) and the Department of Otolaryngology-Head and Neck Surgery (Dr.
Rotenberg), Schulich School of Medicine and Dentistry, University of
Western Ontario, London, Ont. The case described in this article
occurred at the University of Western Ontario.